I have been fighting what I think is Mustard Algae. It was recommended to lower phosphates using phosfree. So I did ... Anyway I tried.
I following the instructions and within 4 hours the pressure on my new cartridge filter was about 30 (started at 10). I continued to let the filter run for 48 hours as instructed.
After 48 hours, my cartridge pressure is 40. I soaked the cartridge in a Filter fresh type product, used a car wash pressure hose to clean it out and put it back on. The pressure started at 10 and then 20, 30 and soon.
How is the heck fire can I unclogged my new $100 cartridge ?
I should have known better because I have been bitten by phosfree before...